Christopher Reeve has never given up his fight for recovery

Superman star Reeve, 50, has been unable to breathe without a respirator for seven years, since he was paralysed from the neck down in a riding fall that damaged his spinal chord.

But on Thursday, doctors at University Hospitals of Cleveland said they had performed the experimental procedure on 28 February.

They said Reeve was now able to breathe for more than two hours without the respirator, compared with 10 minutes before the surgery.

The hope is that, in time, the electrodes will strengthen Reeve's diaphragm muscles enough to allow him to breathe on his own.

In a statement, Dr Raymond Onders, who performed the operation, said initial tests had yielded "impressive results".

Additional benefits

The procedure involves wires running from the electrodes under the skin to a battery pack on the body.

This then sends out electrical currents to stimulate the nerves in the muscles that make the lungs contract.

Over time, Reeve also will be able to speak more normally, Dr Onders said.

The implant could also greatly reduce other medical complications caused by the ventilator, including infections.

The first person to undergo the procedure was a 36-year-old Ohio man, paralysed in a 1998 swimming accident.

He has been breathing with the help of the implants for two years, the hospital said.